1. Field of the Invention
The present invention generally relates to an integrated power unit for a small-type vehicle such as a motorcycle, wherein the integrated power unit includes an engine and a transmission, and has a crankcase which is split into upper and lower sections. The present invention particularly relates to an improved positioning of fastening bosses on a crankcase, the fastening bosses permitting fastening via fastening bolts of an upper crankcase to a lower crankcase.
2. Description of the Background Art
It is well known in the art to provide motorcycle engine having a crankcase which is split so as to provide an upper crankcase portion and a lower crankcase portion. An example of a motorcycle engine which includes such a split crankcase is disclosed in Japanese Utility Model Publication No. Hei 2-13688.
The internal combustion engine disclosed in Japanese Utility Model Publication No. Hei 2-13688 has a configuration wherein a plurality of fastening bosses are provided. The fastening bosses receive fastening bolts for fastening together an upper crankcase portion and a lower crankcase portion. The fastening bosses are positioned on the crankcase such that the fastening bolts are located rearward of a multiple disk friction clutch provided at one end of a transmission shaft, and do not overlap with the multiple disk friction clutch. Instead, the fastening bosses are positioned so that the fastening bolts are spaced rearwards relative to the multiple disk friction clutch in the vehicle front-rear direction.
In this configuration, the fastening bosses, positioned on the back side of the multiple disk friction clutch, are also not overlapping with, but instead are spaced rearward from, a driven gear which is integral with an outer member of the multiple disk friction clutch and which is larger in diameter than the outer member.
The above described configuration makes it difficult to contrive a more compact design of the vehicle body on the rear side, relative to an internal combustion engine mounted on a small-type vehicle.
The present invention has been made in consideration of the above-mentioned drawback in the configuration of a conventional crankcase. Accordingly, it is an object of the present invention to provide an integrated power unit for a small-type vehicle such that, when a split crankcase of the integrated power unit is mounted on the small-type vehicle, a compact vehicle body design is provided on the rear side relative to the integrated power unit.